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<font color='#009900'>// Copyright (C) 2013  Davis E. King (davis@dlib.net)
</font><font color='#009900'>// License: Boost Software License   See LICENSE.txt for the full license.
</font><font color='#0000FF'>#ifndef</font> DLIB_COUNT_BiTS_Hh_
<font color='#0000FF'>#define</font> DLIB_COUNT_BiTS_Hh_

<font color='#0000FF'>#include</font> "<a style='text-decoration:none' href='../algs.h.html'>../algs.h</a>"
<font color='#0000FF'>#include</font> <font color='#5555FF'>&lt;</font>climits<font color='#5555FF'>&gt;</font>

<font color='#0000FF'>namespace</font> dlib
<b>{</b>

<font color='#009900'>// ----------------------------------------------------------------------------------------
</font>
    <font color='#0000FF'>template</font> <font color='#5555FF'>&lt;</font>
        <font color='#0000FF'>typename</font> T
        <font color='#5555FF'>&gt;</font>
    T <b><a name='count_bits'></a>count_bits</b> <font face='Lucida Console'>(</font>
        T v
    <font face='Lucida Console'>)</font>
    <font color='#009900'>/*!
        requires
            - T is an unsigned integral type
        ensures
            - returns the number of bits in v which are set to 1.
    !*/</font>
    <b>{</b>
        <font color='#BB00BB'>COMPILE_TIME_ASSERT</font><font face='Lucida Console'>(</font>is_unsigned_type<font color='#5555FF'>&lt;</font>T<font color='#5555FF'>&gt;</font>::value <font color='#5555FF'>&amp;</font><font color='#5555FF'>&amp;</font> <font color='#0000FF'>sizeof</font><font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font> <font color='#5555FF'>&lt;</font><font color='#5555FF'>=</font> <font color='#979000'>8</font><font face='Lucida Console'>)</font>;

        <font color='#009900'>// This bit of bit trickery is from:
</font>        <font color='#009900'>// http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSet64
</font>
        v <font color='#5555FF'>=</font> v <font color='#5555FF'>-</font> <font face='Lucida Console'>(</font><font face='Lucida Console'>(</font>v <font color='#5555FF'>&gt;</font><font color='#5555FF'>&gt;</font> <font color='#979000'>1</font><font face='Lucida Console'>)</font> <font color='#5555FF'>&amp;</font> <font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font>~<font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font><font color='#979000'>0</font><font color='#5555FF'>/</font><font color='#979000'>3</font><font face='Lucida Console'>)</font>;                           
        v <font color='#5555FF'>=</font> <font face='Lucida Console'>(</font>v <font color='#5555FF'>&amp;</font> <font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font>~<font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font><font color='#979000'>0</font><font color='#5555FF'>/</font><font color='#979000'>15</font><font color='#5555FF'>*</font><font color='#979000'>3</font><font face='Lucida Console'>)</font> <font color='#5555FF'>+</font> <font face='Lucida Console'>(</font><font face='Lucida Console'>(</font>v <font color='#5555FF'>&gt;</font><font color='#5555FF'>&gt;</font> <font color='#979000'>2</font><font face='Lucida Console'>)</font> <font color='#5555FF'>&amp;</font> <font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font>~<font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font><font color='#979000'>0</font><font color='#5555FF'>/</font><font color='#979000'>15</font><font color='#5555FF'>*</font><font color='#979000'>3</font><font face='Lucida Console'>)</font>;      
        v <font color='#5555FF'>=</font> <font face='Lucida Console'>(</font>v <font color='#5555FF'>+</font> <font face='Lucida Console'>(</font>v <font color='#5555FF'>&gt;</font><font color='#5555FF'>&gt;</font> <font color='#979000'>4</font><font face='Lucida Console'>)</font><font face='Lucida Console'>)</font> <font color='#5555FF'>&amp;</font> <font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font>~<font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font><font color='#979000'>0</font><font color='#5555FF'>/</font><font color='#979000'>255</font><font color='#5555FF'>*</font><font color='#979000'>15</font>;                      
        <font color='#0000FF'>return</font> <font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font><font face='Lucida Console'>(</font>v <font color='#5555FF'>*</font> <font face='Lucida Console'>(</font><font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font>~<font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font><font color='#979000'>0</font><font color='#5555FF'>/</font><font color='#979000'>255</font><font face='Lucida Console'>)</font><font face='Lucida Console'>)</font> <font color='#5555FF'>&gt;</font><font color='#5555FF'>&gt;</font> <font face='Lucida Console'>(</font><font color='#0000FF'>sizeof</font><font face='Lucida Console'>(</font>T<font face='Lucida Console'>)</font> <font color='#5555FF'>-</font> <font color='#979000'>1</font><font face='Lucida Console'>)</font> <font color='#5555FF'>*</font> CHAR_BIT; 
    <b>}</b>

<font color='#009900'>// ----------------------------------------------------------------------------------------
</font>
    <font color='#0000FF'>template</font> <font color='#5555FF'>&lt;</font>
        <font color='#0000FF'>typename</font> T
        <font color='#5555FF'>&gt;</font>
    T <b><a name='hamming_distance'></a>hamming_distance</b> <font face='Lucida Console'>(</font>
        <font color='#0000FF'>const</font> T<font color='#5555FF'>&amp;</font> a,
        <font color='#0000FF'>const</font> T<font color='#5555FF'>&amp;</font> b
    <font face='Lucida Console'>)</font>
    <font color='#009900'>/*!
        requires
            - T is an unsigned integral type
        ensures
            - returns the number of bits which differ between a and b.
    !*/</font>
    <b>{</b>
        <font color='#0000FF'>return</font> <font color='#BB00BB'>count_bits</font><font face='Lucida Console'>(</font>a^b<font face='Lucida Console'>)</font>;
    <b>}</b>

<font color='#009900'>// ----------------------------------------------------------------------------------------
</font>
    <font color='#0000FF'>template</font> <font color='#5555FF'>&lt;</font>
        <font color='#0000FF'>typename</font> T
        <font color='#5555FF'>&gt;</font>
    T <b><a name='hamming_distance'></a>hamming_distance</b> <font face='Lucida Console'>(</font>
        <font color='#0000FF'>const</font> std::pair<font color='#5555FF'>&lt;</font>T,T<font color='#5555FF'>&gt;</font><font color='#5555FF'>&amp;</font> a,
        <font color='#0000FF'>const</font> std::pair<font color='#5555FF'>&lt;</font>T,T<font color='#5555FF'>&gt;</font><font color='#5555FF'>&amp;</font> b
    <font face='Lucida Console'>)</font>
    <font color='#009900'>/*!
        requires
            - T is an unsigned integral type or a std::pair that, recursively, eventually
              contains unsigned integral types.
        ensures
            - returns the number of bits which differ between a and b.
    !*/</font>
    <b>{</b>
        <font color='#0000FF'>return</font> <font color='#BB00BB'>hamming_distance</font><font face='Lucida Console'>(</font>a.first,b.first<font face='Lucida Console'>)</font> <font color='#5555FF'>+</font> <font color='#BB00BB'>hamming_distance</font><font face='Lucida Console'>(</font>a.second, b.second<font face='Lucida Console'>)</font>;
    <b>}</b>

<font color='#009900'>// ----------------------------------------------------------------------------------------
</font>
<b>}</b>

<font color='#0000FF'>#endif</font> <font color='#009900'>// DLIB_COUNT_BiTS_Hh_
</font>

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